The correct answer is: Brother.
Deepak is the brother of Ravi, who is the son of Reena. This means that Deepak and Reena are siblings. Siblings are people who have the same parents. In this case, Deepak and Reena have the same father, Atul. Therefore, Deepak is Reena’s brother.
The other options are incorrect because they do not accurately reflect the relationship between Deepak and Reena. Option A is incorrect because Deepak is not Reena’s son. Option B is incorrect because Deepak is not Reena’s brother. Option C is incorrect because Deepak is not Reena’s nephew. Option D is incorrect because Deepak is not Reena’s father.